ShEx schemas at Wikidata reside at https://www.wikidata.org/wiki/EntitySchema:Exxx, but this is not a canonical URI. We should have a canonical URI (prefix), and I guess http://www.wikidata.org/entity/ would do, just as for Items, Properties, and Lexemes.
Once a URI prefix has been found:
- it should be documented whereever necessary
- http://www.wikidata.org/entity/Exxx (or whatever prefix is chosen) should redirect to actual content, as for Items, Properties, and Lexemes.
A canonical URI would likely be required for T225701, and the shex-simple tool could probably make use of it as well for relative URI resolution to a predictable absolute URI.